Applications of the in-line plasma cleaning process

Plasma cleaning equipment comes in two main types: batch and in-line. In-line plasma cleaning uses an automated cleaning method and is suited to large-scale production lines; it saves manpower, reduces labor costs and greatly improves cleaning efficiency, giving it the most pronounced advantages.

In-line plasma cleaning before die attach

Voids in die attach are a common problem in the packaging process. This is because untreated surfaces carry large amounts of oxides and organic contaminants, which lead to incomplete die attach, reduce the heat dissipation capability of the package, and have a major impact on package reliability. Before die attach, in-line plasma cleaning for several tens of seconds with a gas mixture of O2, Ar and H2 can remove organic oxides and metal oxides from device surfaces, increase the surface energy of the material, promote adhesion, reduce voids and greatly improve die attach quality.

In-line plasma cleaning before wire bonding

Wire bonding is the most common and most effective interconnection process between the chip and the external package. Statistics show that about 70% or more of product failures are caused by bonding failures. This is because impurity contamination on the bond pads and thick-film conductors is a major cause of reduced bondability and reliability in wire bonding. Contamination can come from every stage, including the chip, the capillary and the gold wire. If bonding is carried out directly without timely cleaning, defects such as non-stick bonds, bond lift-off and low bond strength will result. In-line plasma cleaning for several tens of seconds with a gas mixture of Ar and H2 can make the contaminants react to form volatile carbon dioxide and water. Because the cleaning time is short, the contaminants are removed without damaging the passivation layer around the bond area. Therefore, in-line plasma cleaning can effectively remove contaminants from the bond area, improve adhesion in the bond area, enhance bond strength and greatly reduce the bonding failure rate.

As microelectronic packaging moves toward miniaturization, surface cleaning requirements are becoming ever higher. The many advantages of in-line plasma cleaning will make it one of the best options for surface cleaning; as the cleaning method with the greatest development potential, it will be applied in more and more fields. At the same time, in-line plasma cleaning is highly beneficial to environmental protection, as it produces no harmful pollutants after cleaning, which makes it all the more important at a time when the whole world places great emphasis on environmental awareness.